1. Background of the Invention
This invention relates to a print circuit substrate which has a high heat-releasing property and yet is little contaminated by noises, thereby ensuring the rapid processing of signals and more particularly to a print circuit board involving a metal core.
2. Description of the Prior Art
Recently difficulties are presented by an increase in the quantity of heat released from the individual parts of an electric circuit and their heat-releasing density due to the high integration of an electric circuit. Consequently, high heat-releasing property is demanded of a circuit substrate. Further, rapid signal processing and suppression of noises are more strongly demanded for improving the performance of electrical implements. The vital importance for the quick signal processing and the maximum elimination of noises is the low permitivity of an insulated substrate, though an electric circuit should also have as low a resistance as possible. The recent trend in manufacturing a high heat-releasing metal core type print circuit board goes toward the process of laminating sheets impregnated with epoxy resin on a metal substrate and coating the laminated mass with a copper foil or spreading resin over the surface of an anodized aluminium sheet and further pasting a copper foil over the laminated mass. The above-mentioned processes have come to be widely accepted in the fabrication of, for example, an electric circuit. However, the recently proposed metal core type print circuit board involves an insulation layer prepared from epoxy resin or anodized aluminium membrane, and consequently has as high a relative dielectric constant as about 4 to 6, thus obstructing application to a high frequency circuit or in the rapid processing of signals. To date, therefore, no metal core type print circuit board has been developed which has a lower relative dielectric constant than 3.